1. Field of the Invention
The present invention relates generally to methods and devices for the selective occlusion of body lumens. More particularly, the present invention relates to methods and devices for applying high frequency electrical energy to vaso-occlusion elements within the body lumen to enhance fibrogenic occlusion of the body lumen.
The selective occlusion of blood vessels in a patient is a part of many modern therapeutic treatments, including the control of internal bleeding, the occlusion of blood supply to tumors, the isolation of diseased body organs prior to removal, the relief of blood pressure in a region of aneurism, and the like. While such procedures rely generally on the blockage of arteries, the selective occlusion of veins is also useful in procedures such as veiniotomy.
The selective occlusion of blood vessels can be achieved by a variety of specific techniques. One such technique involves mechanically clamping or occluding the target site within the blood vessel. For example, in open surgical and endoscopic procedures, the body vessel can be externally clamped and radiofrequency energy applied. While the external procedures can be very effective, it requires external access to the lumen and is unsuitable for endoluminal techniques.
Mechanical endoluminal techniques for selective vessel occlusion are also in use. Such techniques include the use of detachable balloons, embolic and vaso-occlusion coils, and the like to physically block the vessel lumen. Detachable balloons are typically advanced to the vessel site at the end of a catheter and inflated with a suitable fluid, such as saline, x-ray contrast or a polymerizable resin, and released from the end of the catheter. These detachable balloons, however, are difficult to deliver and may not be suitable for permanent implantation unless they are used with the polymerizable resin. In addition, the catheter or the balloon can rupture or release prematurely during filling, leaking monomer resin into the vasculature.
Embolic or vaso-occlusion coils are typically introduced through a catheter in a stretched linear form, and assume a relaxed, helical shape when released into a vessel. One of the limitations of these coils is that recanalization of the occlusion site can occur when the initial blood clot is broken down by the body's natural anticoagulant mechanism (i.e., resorption of the clot). In addition, once the embolic coils are released by the introducer catheter, they are no longer under control and they frequently migrate from the point of initial implantation.
To completely arrest the flow of blood in a vessel and to inhibit recanalization, current methods of coil embolization typically require the use of several embolic coils at the target site in the blood vessel. In this "nesting technique", the embolic coils are deposited within a vessel to create a mechanical "plug". It has been found, however, that the use of several coils does not always prevent recanalization of the blood vessel, particularly in larger, high flow vessels. Moreover, it often takes a relatively long time for the blood vessel to completely occlude. Therefore, the embolic coils may often migrate into a non-target site prior to vessel occlusion, particularly in larger or high flow vessels. Multiple coils are also more expensive than a single coil and they require more time to position within the vessel, thereby further increasing the cost of the procedure and prolonging the patient's exposure to the fluoroscope.
Of particular interest to the present invention, the use of monopolar and bipolar radiofrequency devices has been proposed for the occlusion of body vessels from a surrounding lumen or body cavity. For example, U.S. Pat. No. 5,403,311 describes control of vessels bleeding into a body lumen using electrosurgical electrodes which puncture the vessel from within a larger lumen enclosing that vessel. Catheters for radiofrequency injury and occlusion of the cystic duct are described in Becker et al. (1989) RADIOLOGY 170:561-562 and (1988) RADIOLOGY 167:63-68 and Tanigawa et al. (1994) ACTA RADIOLOGICA 35:626-628. Methods and catheters for electrosurgical endovascular occlusion are described in Brunelle et al. (1980) RADIOLOGY 137:239-240; Cragg et al. (1982) RADIOLOGY 144:303-308; and Brunelle et al. (1983) RADIOLOGY 148:413-415. Such techniques, however, have not generally been useful in large or high flow blood vessels.
For these reasons, it would be desirable to provide improved methods and devices for endoluminal occlusion of body lumens, and particularly of blood vessels, for use in the procedures described above. Such methods and devices should provide effective occlusion of large or relatively high flow body lumens as well as small body lumens. Preferably, the methods and devices will permit the physician to re-access the occlusion site, to correct recanalization and/or to enhance the occlusion of this site to prevent subsequent recanalization of the body lumen.
2. Description of the Background Art
Methods and devices for implanting vaso-occlusive elements, such as coils, in blood vessels and other lumen are described in U.S. Pat. Nos. 5,354,295; 5,350,397; 5,312,415; 5,261,916; 5,250,071; 5,234,437; 5,226,911; 5,217,484; 5,122,136; 5,108,407; 4,994,069; and 3,868,956; and published PCT applications WO 94/11051; WO 94/10936; WO 94/09705; WO 94/06503; and WO 93/06884. Some of the devices described in the above listed patents and published applications suggest passing direct current through the element to enhance blood clotting.
Electrosurgical probes for electrosurgical, electrocautery, and other procedures are described in U.S. Pat. Nos. 5,405,322; 5,385,544; 5,366,490; 5,364,393; 5,281,216; 5,236,410; 4,685,459; 4,655,216; 4,582,057; 4,492,231; 4,209,018; 4,041,952; 4,011,872; 4,005,714; 3,100,489; 2,022,065; 1,995,526; 1,943,543; 1,908,583; and 1,814,791; and published Japanese application 2-121675; published German applications DE 4139029; DT 2646228; and DT 2540968; and published PCT applications WO 95/02366 and WO 93/01758.
A method and system employing RF energy for the direct occlusion of blood vessels and other body lumens are described in co-pending application Ser. No. 08/488,444 filed on Jun. 7, 1995, the full disclosure of which is incorporated herein by reference. See also the patent and publications described in the Field of the Invention above.